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The ICUSB232DB25 USB to RS232 DB9/DB25 Serial Adapter Cable (M/M) lets you connect 9-pin (DB9) or 25-pin (DB25) RS232 serial devices to your laptop or desktop computer through a USB port, as though the computer offered an onboard serial port. The integrated 3-foot (0.9 meter) cable allows it to be connected directly from the serial device to the computer without requiring additional cables.

A cost-effective solution that bridges the compatibility gap between modern computers and legacy serial peripherals, this high quality USB/RS232 Serial Adapter cable ships with a DB-9 to DB-25 adapter for connection to varied serial equipment.

Data Sheets

Frequently Asked Questions

Installation

Starting in High Sierra 10.13, macOS enforces stricter security policies than previous revisions. As a result of these changes, software packages, like those used in this installation, will need to be allowed within the macOS Security and Privacy settings, immediately after the software has been installed, in order for the device to operate.

To allow the software, follow these steps after you've completed installation on your Mac:

Open System Preferences.

Open Security & Privacy.

Click the Allow button near the bottom of the General tab.

Note: The option to allow the software will be available within the Security & Privacy settings for 30 minutes. If the software is not allowed within that time frame, the software must be reinstalled in order for macOS to grant the opportunity to allow it again.

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Some driver installation packages may require you to disable driver signature enforcement in Windows 8, which will allow unsigned driver packages to be installed on your system.

Note: Before you continue, save any open documents and close all open programs.

To disable driver signature enforcement, complete the following:

Press the Windows key + C.

Click Settings > Change PC Settings.

In the left pane, click General.

In the right pane, under Advanced startup, click Restart now.

When your system finishes restarting, complete the following:

Click Troubleshoot > Advanced options > Startup Settings > Restart.

Press 7.

When your computer restarts, driver signature enforcement will be disabled and you can install your drivers.

Note: When you restart your computer after you install your drivers, driver signature enforcement will be enabled again. This does not prevent your newly installed drivers from working, but does prevent any other unsigned drivers from being installed until driver signature enforcement is disabled.

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Some driver installation packages may require you to disable driver signature enforcement in Windows 8.1, which will allow unsigned driver packages to be installed on your system.

Note: Before you continue, save any open documents and close all open programs.

To disable driver signature enforcement, complete the following:

Press the Windows key + C.

Click Settings > Change PC Settings.

In the left pane, click Update & Recovery.

In the left pane, click Recovery.

Under Advanced startup, click Restart now.

When your system finishes restarting, complete the following:

Click Troubleshoot > Advanced options > Startup Settings > Restart.

Press 7.

When your computer restarts, driver signature enforcement will be disabled and you can install your drivers.

Note: When you restart your computer after you install your drivers, driver signature enforcement will be enabled again. This does not prevent your newly installed drivers from working, but does prevent any other unsigned drivers from being installed until driver signature enforcement is disabled.­­­­­­­

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You may need to disable Driver Signature Enforcement in Windows 10 to use some driver installation packages. When you disable this feature, you can install unsigned driver packages on your computer.

Note: Before you continue, save any open documents and close all of your programs. You will need to restart your computer to disable Driver Signature Enforcement.

To disable Driver Signature Enforcement, complete the following:

Click the Windows icon in the taskbar.

Click Power.

Press and hold the Shift key and click Restart.

After your computer finishes restarting, complete the following:

Click Troubleshoot > Advanced Options > Startup Settings > Restart.

Press 7.

When your computer finishes restarting, Driver Signature Enforcement will be disabled and you can install the drivers.

Note: When you restart your computer after you install your drivers, driver signature enforcement will be enabled again. This does not prevent your newly installed drivers from working, but does prevent any other unsigned drivers from being installed until driver signature enforcement is disabled.­­­­­­­

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How to

In Device Manager, under the appropriate heading, confirm that your expansion card is listed and that there isn't an exclamation mark next to it. For example, a USB controller card would be under Universal Serial Bus controllers.

Your USB device is listed according to the name of the chipset. To determine the name of the chipset of your USB device, navigate to www.StarTech.com and look on the Technical Specifications tab for your product.

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To confirm that the Mac OS detects your USB device, complete the following:

Click the Apple icon.

Click About This Mac.

Click More Info or System Report.

Under the appropriate heading, confirm that your USB device is listed and that there isn't an error. For example, a network card would be under Ethernet Cards.

You may need to refresh the System Information page after you plug in your device. To do so, press Command + R with the System Information page open.

Your USB device is listed according to the name of the chipset. To determine the name of the chipset of your USB device, navigate to www.StarTech.com and look on the Technical Specifications tab for your product.

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Troubleshooting

Older applications that use serial communication often use legacy hardware addresses that do not work with PCI, PCIe, or USB to Serial products. We recommend contacting the software provider/support team to check if this is the case.

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When you troubleshoot issues with a serial device, there are some quick tests that you can complete to rule out potential problems. You can test to make sure that the following components are working correctly and are not the source of the issue:

Serial cables

Serial ports

Serial devices

To test your setup components, try the following:

Use the serial cable, serial port, and serial device in another setup to see if the problem is with the components or the setup.

Use a different serial cable, serial port, and serial device in your setup to see if the problem persists. Ideally, you should test a component that you know works in another setup.

When you test your cables, it is recommended that you do the following:

Test each cable individually.

Use short cables when you are testing.

When you test the serial ports and serial device, it is recommended that you do the following:

Press the Windows key + R, type devmgmt.msc, and press Enter to open Device Manager. Check to see if your device is listed under Ports (COM & LPT).

Make sure that the COM port number is the correct number for the serial device and that the software being used to connect the computer to the serial device uses the correct COM port number.

If the device is listed with an error, follow the instructions on the website to reinstall the drivers.

Note: Some serial devices work only if the COM port number is between a certain range. For example, COM1 to COM4.

Note: To open a telnet session on the COM port, you need a telnet client like PuTTY or Hyper Terminal. Windows XP comes with Hyper Terminal.

When the session is open, anything you type into it you should see. The loopback test fails when you cannot see what you are typing.

If the loopback test fails, make sure that the serial cable or gender changer that you are using works and that the adapter is in the correct port.

You can check multiple ports at the same time by opening multiple sessions, putting the loopback adapter on one port, and trying to type into each session. When you can see what you are typing, you know that the COM port is working and you can see which port number the physical serial port is. Close the window for the port that you just tested to speed up the testing of the remaining serial ports.

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Common Issues

Use a USB to Serial product that features COM Port Retention. These products will store settings that are unique to the connected device in non-volatile memory, allowing you to retain the desired settings regardless of the USB Port to which the adapter is connected.